High frequency generator



Aug. 6, 1940. w. J. POLYDOROFF HIGH FREQUENCY GENERATOR Original FiledMay '7, 1951 89? nwomu P59. V 7 6 5 4 3 2 I FR EGUENCY ATTORNEY PatentedAug. 6, 1940 UNITED 'STATES man FREQUENCY GENERATOR Wladimir J.Polydorofl, Wilmette, m, assign: to Johnson Laboratories, Inc., Chicago,111., a corporation of Illinois Original application May 7, 1931, SerialNo. 535,606, now Patent No. 2,113,603, dated April 12, 1938. Divided andthis application June 17, 1937, Serial No. 3, 1939 12 Claims.

The invention relates to variable inductance devices, which, among theirother advantageous uses, may be employed as parts of radio-frequencygenerator circuits.

able inductance devices herein disclosed. include inductance coils andferromagnetic cores adjustable relatively thereto, the combination beingsuch that at all high frequencies, maximum permeability oi the coreconsistent with the desired losses involved in any case, may beattained.

One object of the invention is to provide a new and useful tuning devicesuitable for use in hiZh-II'BQHQDOY circuits, of the variable-inductancerather than the variable-capacitance type,

and which will therefore avoid the usual disadvantages encountered withthe latter type. Among the disadvantages of systems employingvariable-capacitance tuning, which it is one of the objects of thepresent invention to overcome,

gois the non-uniformity of the performance of the circuits throughoutthe tuning range. The present invention provides a tuning device whichwhen employed at radio frequencies, permits tuning a circuit over adesired range of frequencies, while at the same time maintaining theperformance of the circuit substantially constant.

Additional objects and advantages of the present invention will beapparent from what is to follow. Among these may be mentioned theprovision of tuning devices which are not subject to detuning or otherdifliculties due to mechanical vibrations, and which are inherentlyincapable of the microphonic action by which sustained audio-frequencyoscillations frequently arise in capacitance-tuned systems. Also to benoted are the advantages of extreme compactness, ease of assembly, andthe ease and effectiveness of shielding to avoid the effects ofextraneous electromagnetic and/or electrostatic fields.

The application is a division of my application, original Serial No.535,606, filed May 7, 1931, now Patent No. 2,113,603, issued April 12,1938, in which are disclosed various advantageous embodiments of myinvention.

In the present application, .the specific object is to providehigh-frequency generating apparatus tuned by a ferromagnetic core havingunique advantages over the capacitance-tuned high-frequency generatingapparatus of the prior art.

The core embodied in the present device may -be one of the compressedpowdered-iron type which is fully described in my United States PatentNo. 1,982,689 issued December 4, 1934, and which may have varyingferromagnetic density along its axis as disclosed therein.

The improved vari-.

148,789. ltenewed June The invention will be best understood, ifreference be-made to the accompanying drawing in which:

Figure 1 is a sectional view showing a tuning device which may beemployed for the purpose of 6 the invention;

Figures 2 to 5 inclusive are schematic diagrams of high-frequencygenerators, constructed in accordance with the invention; and

Figure 6 is a graph indicating results attained by the use of thecircuits of Figures 2 to 5 inclu- S1Ve.

Specifically, the presentinvention involves a radio-frequency inductancedevice having a core, suchas is described in my aforesaid patent, and soarranged in any one of various radio-frequency generator circuits,thattuning of that circuit may be eifected by adjustments of the corewith the attainment of the several advantages hereinafter indicated.

Referring to Figure 1, l is a compressed ferromagnetic core preferablyhaving an annular cavity 2 that is adapted to receive a tube 3 carryingan inductance coil 4, and, if desired, an additional winding 4a.

As shown, the core I is movable, while the tube 3 carrying either thecoil 4 or the coils 4 and 4a, is fixed, to thereby effectuate variationsof inductance in the device 5, which, as herein revealed, maybe employedfor tuning radio-frequency generator circuits of difierenttypes.

Telescoping open-ended shields 6, 1 of any suitable material may .beemployed in order at all times to exclude external inductive influences.Such shields 6, disposed around the cores, are optional and aredesirable only when thorough shielding is required.

In order to produce an effective permeability of 7.5 by a given core,the coil used with the core should have a ratio of length to diameter ofsubstantially 1.5 to 1. If greater permeability is required, the coremay be lengthened, to correspond with a coil of increased ratio oflength to diameter, for example, 2 to 1, in which case the coil, beinglonger, will have less inductance rela tive to resistance. On the otherhand, if ferromagnetic material having greater permeability is used forthe core,.the length of the coil relative'to its diameter may bereduced. By the term effective permeability (,ui) I mean the ratio ofthe inductance of a coil having a ferromagnetic core to the inductanceof the same coil with an air core, without regard to whether the core isclosed, or whether or not the core encloses all of the flux linesthrough the coil.

65 I --being included in the timed plate circuit.

It may be advantageous to keep the electrical properties of the circuitat certain optimum condltions, which are satisfied when the ratio ofinductance to resistance, or L/R, of that circuit is kept constant atall frequencies to which the circuit may-be tuned.

At a frequency f0, where the core is withdrawn, the corresponding ratioLo/Ro of the coil alone is responsible for the successful operation ofthe circuit." when the core is partly moved in, certain losses areintroduced and the inductance is increased to Loni. The core is soconstructed that, for each new value of inductance Low, 9. new value ofeffective resistance Rain is obtained in such manner that the value ofLo n/Flinn at any new frequency ,f1, is substantially equal to vfrequencies.

the original value Lo/Ro of the coil atlfrequency f0. By theresistance-increase factor in, Imean the ratio of the'effectiveresistance of a coil having a ferromagnetic core measured at frequencyany frequency to which the circuit is tuned.

Figures 2, 3, 4 .and show the applicationof the iron-core variableinductance device to vari-' ous types of frequency-"generating apparatusknown in theart as thermionic relay oscillators. Figure 2 shows anoscillator including a thermionic relay A, its grid and plate beingconnected to the opposite ends of coil L, the inductance of which isvaried by relative movement of a ferromagnetic core to produceoscillations of various Capacitors C1 and C2, preferably of. equalvalues, serve as voltage-dividing means with respect to the cathode ofthe thermionic relay A. Regulating resistor R1 may be employed tofurther control the current in the circuit L, 01', Ca,- its value beinginitially so chosen asto equalize the current outputiat differentfrequencies.

Figure 3 represents apparatus wherein a center tap of the inductancedevice L1, L2 is provided for the cathode of thermionic relay A. Avariation of Figure 3 is represented in F re 4 where the plateinductance L1 only is tuned to generate the desired frequencies, theinductance Ls not Figure 5 represents anotherform of oscillator, whereina circuit L1, C1, R1 is tuned by an inductance device L1 having aferromagnetic core, the circuit operating on the principle known as 'adynatron oscillator.

other by the core movement, thus producing variable excitation of theoscillator to equalize the output current at different frequencies.Figure 6 graphically represents operating conditions of the describedoscillators. Curve a shows the variation of current output 01'- theoscillator 01 Figure 2 when resistor R1 is shortcircuited, and curve bshows the variations of current of the same oscillator when resistor R1-is included in the circuit so as to obtain substantially uniform outputof. current at different frequencies. Curves c, d and e correspondingly,show variations of current with frequency in the from and, movablerelatively to said coil, combined with a resistance of. the order of thehighfrequency resistance of the device at its maximum inductance,whereby the total effective impedance of said combination may be adaptedfor use in a tunable oscillator circuit.

2. A thermionic oscillation generator for use at high frequencies,including an inductance coll,

a'movable core of comminuted ferromagnetic material for varying theinductance of said coil, and fixed capacitances of predetermined values,said core being such that the L/R. ratio of said coil is maintainedsubstantially constant at different frequencies generated by saidgenerator, and that the oscillatory current frequency increases.

3. A thermionic oscillation generator for use at high frequencies,including an inductance coil, a movable core of comminuted ferromagneticmaterial for varyingthe inductance of said coil, fixed capacitances, anda resistor of such value that the current in said oscillator ismaintained increases with substantially constant while the resistance'ofthe ically more affected than the other by said core and a substantiallyconstant oscillatory current at diflerent frequencies is-maintained.

5-. A variable high-frequency oscillation generator, including athermionic vacuum tube having a grid, a cathode and a plate; a resonantcircuit having first and second capacitors connected in series and aninductance coil in shunt with said capacitors; and means for varying thefrequency and simultaneously controlling. the

amplitude of the output of said generator includ-- -ing a ferromagneticcore movable relatively to said inductance coil, said resonant circuitincluding a resistance of the order of the high-frequency resistance'ofthe coil and core combination at the maximum inductance of said coil, a

' connection from the high-potential terminal of said circuit to saidplate, a connection from the low-potential terminal'of saidseries-connected capacitors through a third capacitor to said grid andthrough said third capacitor and a resistor to said cathode, and aconnection from the junction of said first and second capacitors to saidcathode.

6. A variable high-frequency oscillation gen- Q erator, including athermionic vacuum tube having a grid, a cathode and a plate; a resonantcircuit having a first capacitor and an inductance coil having a tapconnected to said cathode, a first terminal connected to said plateand asec, ond terminal connected through a second capacitor shunted by aresistor to said grid; and means for varying. the frequency andsimultaneously controlling the amplitude of the output of said generatorincluding a ferromagnetic core movable relatively to said inductancecoil, which varies the coupling between the grid and plate portionsthereof, said resonant circuit including a resistance of the order ofthe high-frequency resistance of the coil and core combination at themaximum inductance of said coil.

7. A variable high-frequency oscillation generator, including athermionic vacuum tube having a grid, a cathode and a plate; a resonantcircuit having a first capacitor and an inductance coil having a tapconnected to said cathode, a first terminal connected to said plate anda second terminal connected through a second capacitor shunted by aresistor to said grid; and means for varying the frequency andsimultaneously controlling the amplitude of the output of said generatorincluding a ferro-magnetic core constructed to maintain the ratio ofinductance to resistance in said resonant circuit substantially constantand movable relatively to said inductance coil, which varies thecoupling between the grid and plate portions thereof.

8. A variable high-frequency oscillation generator, including athermionic vacuum tube having a grid, a cathode and a plate; a resonantcircuit having a first capacitor and an inductance coil having a tapconnected to said cathode, a first terminal connected to said plate anda second terminal connected to said grid; and means for varying thefrequency and simultaneously controlling the amplitude of the output ofsaid generator including a ferro-magnetic core movable relatively tosaid inductance coil, which varies the coupling between the grid andplate portions thereof; said resonant circuit including a resistance ofthe order of the high-frequency resistance of the coil and corecombination at the maximum inductance of said coil.

9. A variable high-frequency oscillation generator, including athermionic vacuum tube of the dynatron type and having a grid, a plateand a cathode; a resonant circuit having a capacitor and an inductancecoil having a first terminal connected to said plate and a secondterminal connected through a resistor and a source of direct-currentpotential to saidcathode; a connection through a second source ofdirect-current potential from said cathode to said grid; and means forvarying the frequency and simultaneously controlling the amplitude ofthe output of said generator including a ferromagnetic core movablerelatively to said inductance coil, said resonant circuit including aresistance of the order of the high-frequency resistance of the coil andcore combination at the maximum inductance of said coil.

10. A variable high-frequency oscillation generator, including athermionic vacuum tube of the dynatron type and having a grid, a plateand a cathode; a resonant circuit having a capacitor and an inductancecoil having a first terminal connected to said plate and a secondterminal connected through a resistor and a source of direct-currentpotential to said cathode; a connection through a second source ofdirect-current potential from said cathode to said grid; and means forvarying the frequency and simultaneously controlling the amplitude ofthe output of said generator including a ferromagnetic core constructedto maintain the ratio of inductance to resistance in said resonantcircuit substantially constant and movable relatively to said inductancecoil.

11. A variable high-frequency oscillation gen- .erator, including athermionic vacuum tube having a grid, a cathode and a plate; a resonantcircuit having first and second capacitors connected in series and aninductance coil in shunt with said capacitors; and means for varying thefrequency and simultaneously controlling the amplitude of the output ofsaid generator including a ferromagnetic core constructed to maintainthe ratio of inductance to resistance in said resonant circuitsubstantially constant and movable relatively to said inductance coil,9. first resistor in series in the low-potential side of said resonantcircuit, a connection from the high-potential terminal of said circuitto said plate, a connection from the low-potential terminal of saidseriesconnected capacitors through a third capacitor to said gridand'through said third capacitor and a second resistor to said cathode,and a connection from the junction of said first and second capacitorsto said cathode.

12. A variable high-frequency oscillation generator, including athermionic vacuum tube having a grid, a cathode and a plate; a resonantcircuit having a first capacitor and an inductance coil having a tapconnected to said cathode, a first terminal connected to said plate anda second terminal connected through a second capacitor shunted by afirst resistor to said grid; means for varying the frequency andsimultaneously controlling the amplitude of the output of said generatorincluding a ferromagnetic core constructed to maintain the ratio ofinductance to resistance in said resonant circuit substantially constantand movable relatively to said inductance coil, which varies thecoupling between the grid and plate portions thereof; and a1secondresistor in series in said resonant circuit.

WLADIMIR J. POLYDOROFF.

